I've been reloading for many years but never ran across this before.
When tumbling my 30 carbine brass I found a black waxy substance on the cases. These were factory Aguila rounds fired from my Blackhawk revolver.

I had previously tumbled these cases in Lyman green treated cob. The residue looked like a light green corrosion on the surface of the brass. When I ran them a second time in long grain rice (test media, works great!) the green dust was removed leaving the waxy black stuff. I have since tumbled them in a batch of new untreated walnut shell and the black stuff remains.

So, three multi-hour tumblings in three different medias and I still have stuff on the cases. The strange thing is that I can scrape it off with a fingernail. Tumbling media doesn't impact cases with any force so it won't push this stuff off.
I just opened another box of the ammo as I was writing this and there does not seem to be any wax, sealant, or lube on the unfired ammo.

This batch of cases was mixed with 45 Colt, 38 spl, and 7tcu as a test for tumbling with long grain rice. All the other cases came out nice and clean so I can only assume the problem is with the gun.

All I can think of is to clean the revolver better than it's ever been cleaned before and run more ammo through it.

Have you guys ever run across anything like this? I'd expect it with the 45 Colt with all the wax and lead it sees but I have no problems there.

For the record, there was ZERO DUST with the rice. The same batch of rice has now tumbled several hundred cases with great results. The walnut, corn cob, and Lyman stuff is all going in the trash. Rice is here to stay.

If it feels like wax it probably is. The wax would pick up dust from the tumbling media for it's color.

Since you didn't notice the problem when you were shooting, where it should have picked up soot on the wax, I'm going to guess the contamination happened after shooting and before cleaning. Any chance the fired brass got into a bag with some lubricated cast bullets?

All of my fired cases go into a bag at the range. When I get home it's all dumped into a tin can.
Several of the cases have a stretched out U shape of residue. It starts near the rim, goes up towards the mouth, and curves over a bit before heading back towards the rim. Other cases have a glob of it near the mouth.

Have you let the case cool and felt for the wax before leaving the range? After cleaning the gun thoroughly, that would be my next step. Well, no, actually my next step would be to pull one and look for anything strange, but not finding such, then I'd be checking it at the range.

I am guessing that it is case lube. I load .30 Carbine, and case lube is needed even with carbide dies due to the cases taper. Tumble in walnut shell media with a touch of NuFinish for a good while. I wipe mine off with a damp cloth before I drop them into the tumbler. It cuts the time they need in the tumbler greatly. Spray on lanolin based lube does it the worst. I use Lee Case lube on .30 Carbine, and .45-70 it comes off easier.

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No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.

I have had similar problems when using nufinish and corncob media , Its time to toss the rice if you have added nufiish to it . you may well have to much nu finish in the mix now . Brake cleaner will take that right off or new clean corb media . I switched to stainless media a couple of years ago and think its great

I would suggest that it residue left by the green polish in the original media that has been congealed into the oil from the rice. I tried the rice a couple of times and quit because of the oily residue it left.
And because of the black goo from the cases it did not look very tasty when my wife cooked it.

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Education teaches you the rules, experience teaches you the exceptions (Plagiarized from Claude Clay)

Its either one of two things or a combo of the two. Wax as in case sizing lube. Way to much polishing compound in the media, NuFinish. I have had the same, I now rinse all my cases after sizing in gas. It quick and the dry in only a few minutes. Ya, I know gas is flammable, but filling my lawn mower can also be dangerous if done next to the burning leaves.

This brass was tumbled in the Lyman green corn cob. No additive was used.
The cases had a green residue on them. At the time I thought it was some sort of corrosion. I stuffed the cases in a ziplock bag and put it away.

Fast forward several months.

I was having good results with raw long grain rice treated with a small amount of Frankford Arsenal case polish. I tried tumbling these cases again. The rice took off the green dust but left the black stuff that was under the dust.

I'm trying to figure out where the waxy stuff came from. It is not on any of my other brass. That eliminates the media. My 45 Colt, 45 ACP, 38 spl, 7 TCU, 300 WM, 454, 460, 308, and 22-250 cases are all free of this stuff.
It is not the tumbling media. All the rice has done is remove the dust left behind by the Lyman green stuff.

This second batch was tumbled for a longer time in the rice and it looks great other than the nasty stuff. It's cleaner inside than what I used to get with the Lyman product.

Again, these were factory loads. None of them had ever seen my loading bench. I can not feel any residue on new ammunition from the same case.

What I meant was, if you clean the gun well, go to the range, fire the new ammunition, then feel the fired cases after ejection, do you feel the stickiness? You could also sprinkle a little chalk dust from a chalk line on the cases to see if it sticks anywhere.

If not, try sprinkling chalk dust inside the case to look for bullet sealant, as 243winxb was suggesting. If you find it, that could conceivably migrate from inside to out during cleaning, though I'd expect the distribution to be more even.

You could try a pre-cleaning rinse in mineral spirits to see if anything dissolves.

I have the feeling that if this was related to the tumbling media that all of the 30 carbine would have it (a little more than half are bad) and the hundreds of other cases I've tumbled in the exact same media would be affected.

If anything, I'd expect to see it on the 45 Colt due to the bullet lube but those cases came out clean while being tumbled at the same time as the first batch of 30 carbine.

I have a range day coming up on Saturday. I'll be sure the gun is as clean as possible. Then, I'll tumble some new ammo and pack it separately from the other stuff. When I get to the range, I'll fire the cleaned ammo and then the uncleaned ammo and keep the cases separate. I'll see if either set has any residue.

I don't know that it would be lube going backwards. I don't have that problem with lead in my 45 Colt, heavy Colt, or 454 loads. I shot plenty of gas checked lead out of my 460 and never had that problem.

Its just a thought, as I said I've only experienced it with 30 cal. carbine. I also cast and shoot .32 ACP, .380, 9mm, 9mm Largo, 9mm Makrov, 38 Spec, 357 Mag, 45 ACP, 30/06 gas checked, 40 S&W, 7.62 x 39 gas checked. None of these give me this problem. All are lubed with my own lube mix.

I've got to think about what you're saying. It's certainly the case that the gas system is still pressurized at the time the bullet has cleared the muzzle, so you expect it to 'exhale' a little through the gas port after the barrel pressure drops. If that gas contains some vaporized wax, it might deposit in the barrel and, to a lesser extent, become part of the blowby around the case as it starts to extract. The port is certainly close enough to the chamber. So, maybe you're on to something.

That happen to to me. I didn't let the liquid polish additive mix long enough with the media before adding the brass. The media was old also with alot of dust or brass contamination(black dust). I have since replaced the media with the lyman green corn cob stuff. Works great now. Only tumble for an hour and the brass looks better than factory clean.

I've got to think about what you're saying. It's certainly the case that the gas system is still pressurized at the time the bullet has cleared the muzzle, so you expect it to 'exhale' a little through the gas port after the barrel pressure drops. If that gas contains some vaporized wax, it might deposit in the barrel and, to a lesser extent, become part of the blowby around the case as it starts to extract. The port is certainly close enough to the chamber. So, maybe you're on to something.

Interesting. In that instance it's maybe the pitch seal that remains in the case around the inside of the neck after firing. If you use mineral spirits, that, for sure, will dissolve it. It is like tar (actually it is tar; i.e., asphaltum), though it eventually hardens again as the mineral spirits dry up.

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